Background

Vascularized bone grafts are when we take a segment of bone from one part of the body and transfer it to another, while maintaining the blood supply (artery and vein).

Causes

Bone loss can be due to infection, trauma, radiation, cancer, avascular necrosis, or various types of fracture nonunions. The bone involved can be as small as the lunate in the wrist, to the large pelvic bones, or long bones such as the humerus, femur or tibia.

Symptoms

In the case of a non-healing fracture (“nonunion”) there can be pain, swelling and instability. Cases of avascular necrosis often present with swelling, pain and restricted motion at the affected joint. In the setting of infection, a draining wound or sinus can be present.

Diagnosis

Physical examination is important to assess the surrounding soft tissues, their pliability, associated wounds, radiation damage, presence of infection. If the involved body part is an extremity, a thorough pulse exam is essential. The sensation of the affected extremity will help guide the decision making as well. Xrays are part of the basic evaluation. Advanced imaging such as MRI and CT scan are often required to better understand the skeletal anatomy and soft tissue envelope.

Treatment

Depending on the bone involved, there are often several treatment options, including using non-vascularized bone which is taken either from the patient or a cadaver; alternatively, vascularized bone can be indicated.

The advantage of this sort of bone transfer, or bone graft, is that the bone is alive. This can help promote better healing, especially in cases where trauma or infection (for example) have led to an impairment of the blood supply.

In the following sections, we provide examples of various types of bone grafts and their applications.

Scaphoid nonunion

Background

The blood supply to the scaphoid bone in the wrist is considered to be tenuous. This can lead to issues with healing when a fracture occurs. Another cause is that scaphoid fractures can often go undiagnosed and patients resume their usual activities untill pain, swelling and stiffness result, at which point in time xrays reveal a scaphoid nonunion.

Causes

Scaphoid fractures most often occur after a fall on an outstretched hand. The blood supply of the scaphoid bone being more limited compared to other bones, the fracture may not heal. The exact location of the fracture also plays a role. Furthermore, if a fracture goes undiagnosed, and the patient continues to use their wrist without restriction, then the excessive motion at the fracture site can contribute to a non-union.

Symptoms

A scaphoid nonunion leads to pain, swelling of the wrist with use, restricted motion and can progress to a pattern of wrist arthritis called SNAC wrist (Scaphoid Nonunion Advanced Collapse).

Diagnosis

Physical examination reveals tenderness in the so-called “anatomic snuffbox”, pain on axial loading of the thumb. Wrist motion can be limited. Xrays are the first imaging modality that is ordered. If a nonunion is suspected, Dr. Dowlatshahi routinely obtains an MRI and a CT scan for preoperative planning. A 3D model can help plan the bone grafting procedure.

Treatment

Depending on the fracture pattern, patient age and comorbidities, and the status of the remainder of the wrist, several options are considered:

watch and wait.
minimally invasive placement of a cannulated headless compression screw.
screw + cancellous bone graft.
screw + corticocancellous bone graft.
screw + vascularized corticocancellous bone graft.

Here is the example of a 15 year old patient with a scaphoid nonunion with substantial collapse of the scaphoid called “humpback deformity”. He was treated with a non-vascularized bone graft from the iliac crest.

Immediate postoperative result:

1 year postoperative result is shown here after hardware removal. He has full, painless range of motion and his scaphoid is indistinguishable from a normal, uninjured bone.

The medial femoral condyle flap is a powerful vascularized bone graft that is taken from the knee. The knee joint itself is not violated, therefore the morbidity to knee function is usually minimal.

Here is an example of a young active patient with a scaphoid nonunion which Dr. Dowlatshahi treated with a free medial femoral condyle flap.

Preop:

Immediately postoperatively, the graft is clearly visible with the cannulated headless compression screw in place.

6 months postoperatively, the fracture is no longer visible. The bone graft is well incorporated. A section of the screw is visible.

When the entire proximal pole of the scaphoid is necrotic or if prior attempt at screw fixation has resulted in a proximal pole that isn’t usable, the entire proximal pole of the scaphoid can be replaced using bone from the knee. In this case, a small opening is made in the knee joint and a section of cartilage is taken together with bone and the accompanying blood vessels. This procedure is called free Medial Femoral Trochlea Flap (MFT). Here is an example.